Service engine soon light

I have a 2001 Ford ZX2, 4 cylinder. The service engine soon light came on about 400 miles ago. I had a check run and it came up with a #P0171. Says my gas is running lean or rich. Probable causes are mass air flow sensor, oxygen sensor or suspect fuel pressure. With that code # can it be narrowed down to one thing? I hate to spend money doing it one by one until it is fixed.

Code P0171=System Too Lean (Bank 1).

Whenever this code comes up the first thing to try is cleaning the MAF sensor with MAF sensor cleaner. If the hot wires in the MAF sensor has debris on them, it effects the signal to the computer making it think not as much air is being drawn into the engine. The computer then compares the signal from the MAF sensor to the signal it gets from the upstream O2 sensor. If the signal from the O2 sensor doesn’t compare to the signal from the dirty MAf sensor, the computer thinks the engine is running too lean and sets this code.


OK, thanks. I bought some cleaner and will get to it in a few days. Have to figure out where the maf sensor is, think I have it nailed down to 1 of 2 gadgets. Do I have to remove the whole sensor? That’s what the cleaner says to do, was wondering if I could just spray it on and try that 1st. Is there anything I need to be aware of before I do this? If I screw it up a new sensor costs $125 that I don’t have.

ya, you can do all sorts of damage, so let a pro do it or pay a lot more in the end

The MAF will be in the air intake - big black rubber tube w/ the air filter at one end and the throttle/intake manifold at the other. The heart of the thing is two tiny little wires that sit in the middle of the incoming air stream - those are what need to be cleaned.

Based on the way you’re talking about things, I’d say that you should probably buy a repair manual and spend some time getting to know your way around under the hood. If you are determined to clean the MAF - paddfoot is right - it is an expensive little device but can’t take much abuse. Do a little extra web research on MAF cleaning before you mess with. I’ll bet someone has posted some video somewhere.